Add support for Style Guides API

The Crowdin API introduces a new **Style Guides** section. API client libraries should be updated to expose the Style Guides endpoints so that consumers can manage style guides (list, create, get, edit, delete) via the SDK.

**References:**
- [Style Guides](https://support.crowdin.com/developer/api/v2/#tag/Style-Guides)

Start with the Crowdin API v2 Style Guides reference linked in the issue and inspect the existing Go client patterns for other CRUD resources. Implement SDK coverage for listing, creating, retrieving, editing, and deleting style guides, then verify each endpoint against the API documentation.

Written by the indexing model from the issue text.